There are currently X monsters in the game.
They are in order of appearance. (If you follow the main questline)
Drudge
Drudge Seer
Drudge Nightmare Mage
Drudge Beater
Orc
Blood Orc
Orc Chopper
Orc Hag
Orc Hag
Orc Champion
Orc Stabber
Wild Pig
Boar
Dire Boar
Hel Boar
Boar Spirit
Slime
Bomb Slime
Speed Slime
Bull Slime
Mama Slime
Ink Wraith
Ichor Wraith
Nightmare Wraith
Immortal Wraith
Golem Pawn
Golem Knight
Headless Knight
Golem Bishop
Golem Rook
God of Boars
Golem King
Drudgor
Drudgor
Grekk
Vataneba
Uamuleth
Slime Prince
Blorpx
Portal Seal
Nightmare Orc Stalker
Nightmare Hag
Rainbow Slime
Big Mama Slime
Unterdrudge
Drudge Magier
Blitz Drudge
Uberdrudge
Decoration
Bomb Pig
Negaboar
Dark Bishop
Dark Knight
Dark Headless
Skeleton
Zombie
Fat Zombie
Exploded Fat Zombie
Rotting Warrior
Night Magier Drudge
Dark Blitz Drudge
Ghost
Imp
Ashen Cultist
Horned Demon
Blue Demon
Horned Skeleton
Mana Zombie
Exploded Mana Zombie
Dark Wraith
Primal Slime
Floating Eye
Splitting Slime
Goat Slime
Sprayer Slime
Lazy Eye
Splitting Slime
Primordial Slime
Sacrificial Cultist
Blue Firestormer
Reborn Cultist
Faceless Soldier
Faceless Magus
Quiet Man
Unformed
Fragile Wailer
Chatter Pile
Wailing Mass
Wailing Nightmare
Fragile Nightmare
Nightmare Mage